Tripedal flexure member and load/torque measurement systems using same

Abstract

A flexure structure comprising the unitary combination of three modified S-shaped beams arranged in parallel and sharing common top and bottom structures. The outside beams are oriented alike in one direction while the inside or center beam is oriented in the opposite direction. The outside edge surfaces of the beams are flat and are instrumented with strain sensors connected in bridge circuits.

What is claimed is: 
     
       1. A tripedal flexure comprising the unitary combination of:
 a pair of substantially S-shaped outside beams with reversely curved upper and lower portions with edge surfaces; and 
 a single substantially S-shaped center beam having reversely curved upper and lower portions with edge surfaces; 
 the upper and lower portions of the outside beams being oriented in the same direction whereas the upper and lower curved portions of the center beam are oriented in the opposite direction; 
 the beams being spaced apart from one another along the upper and lower curved portions but integrally joined to form a common top structure and a common base structure; wherein 
 each of the beams provides strain concentration areas. 
 
     
     
       2. The flexure defined in  claim 1 , further including strain sensing elements applied to at least some of said areas. 
     
     
       3. The tripedal flexure defined in  claim 1  wherein each of said outside and center beams has opposite exposed edge surfaces, the exposed edge surfaces of the center beam being oriented opposite to the edge surfaces of the outside beams; the edge surfaces on the inside of the S-portions being curved whereas the edge surfaces on the outside of the S-portions are flat. 
     
     
       4. A tripedal flexure as defined in  claim 3  wherein said strain sensing elements are variable resistors applied to said flat edge surfaces. 
     
     
       5. A tripedal flexure as defined in  claim 3  wherein all of the flat edge surfaces areas are provided with variable resistance strain sensing devices thereby to allow said flexure to measure all or any of tension forces, compression forces and/or torque. 
     
     
       6. A flexure as defined in  claim 1  wherein the flexure is made from a single piece of stock. 
     
     
       7. A force and/or torque sensor comprising:
 three substantially identical S-shaped flexure beams including a center beam oriented east to west and two side beams oriented west to east, all of said beams having outside edge surfaces; 
 the three S-shaped beams being arranged parallel to one another and laterally spaced apart but integrated structurally by a common mounting structure on one axial end and a common loading structure on the other axial end; 
 the three beams being structurally and flexurally separated from one another other than at the mounting and loading structures; and 
 the edge surfaces of one or more of the three beams being instrumented to produce electrical signals when loaded in one or more of tension, compression and torque. 
 
     
     
       8. The force and/or torque sensor defined in  claim 7  wherein the center beam is approximately twice the thickness of the outside beams. 
     
     
       9. A force and/or torque sensor as defined in  claim 7  wherein the overall structure has a height on the order of 0.158″, a width on the order of 0.118″ and a depth on the order of 0.078″. 
     
     
       10. A force and/or torque sensor as defined in  claim 7  wherein the entire structure is manufactured from a single piece of stock using material selected from the group consisting of stainless steel, Inconel and aluminum. 
     
     
       11. A force and/or torque sensor as defined in  claim 7  wherein the edge surfaces consist of flat outside edge surfaces and curved inside edge surfaces on each of the substantially S-shaped flexure beams.